Competitive interactions in Escherichia coli populations: the role of bacteriocins

Abstract

Explaining the coexistence of competing species is a major challenge in community ecology. In bacterial systems, competition is often driven by the production of bacteriocins, which are narrowspectrum proteinaceous toxins that serve to kill closely related species, providing the producer better access to limited resources. Bacteriocin producers have been shown to competitively exclude sensitive, nonproducing strains. However, the dynamics between bacteriocin producers, each lethal to its competitor, are largely unknown. In this study, we used in vitro, in vivo and in silico models to study competitive interactions between bacteriocin producers. Two Escherichia coli strains were generated, each carrying a DNA-degrading bacteriocin (colicins E2 and E7). Using reporter-gene assays, we showed that each DNase bacteriocin is not only lethal to its opponent but, at lower doses, can also induce the expression of its opponent's toxin. In a well-mixed habitat, the E2 producer outcompeted its adversary; however, in structured environments (on plates or in mice colons), the two producers coexisted in a spatially 'frozen' pattern. Coexistence occurred when the producers were initiated with a clumped spatial distribution. This suggests that a 'clump' of each producer can block invasion of the other producer. Agent-based simulation of bacteriocin-mediated competition further showed that mutual exclusion in a structured environment is a relatively robust result. These models imply that colicin-mediated colicin induction enables producers to successfully compete and defend their niche against invaders. This suggests that localized interactions between producers of DNA-degrading toxins can lead to stable coexistence of heterogeneously distributed strains within the bacterial community and to the maintenance of diversity.

Characterization of Epidemic IncI1-Iγ Plasmids Harboring Ambler Class A and C Genes in Escherichia coli and Salmonella enterica from Animals and Humans

“…All other plasmids of the present study lacked the cib and imm genes. Expression of colicins can benefit the bacterial host by causing lethality to related enteric bacteria that would otherwise compete for scarce nutrients under conditions of stress (35).…”

Interaction between the Microbial Community and Invading Escherichia coli O157:H7 in Soils from Vegetable Fields

“…The G Ϫ /G ϩ ratio can be an indicator of the structure of soil bacterial communities, suggesting that the structure of the bacterial communities affects the survival of E. coli O157:H7. In bacterial communities, bacteria can produce bacteriocins, which can inhibit and even kill other strains or species with a similar niche or limit the advance of neighboring cells (36). Furthermore, bacteriocin production may be more important in the invasion of niches than in obtaining nutrients (37).…”

The Bacillus cereus Group Is an Excellent Reservoir of Novel Lanthipeptides

“…The prevailing view is that the production of antimicrobial compounds might facilitate the competition of a producer and be a competitive advantage in certain environment (33,34). The bacteria of the B. cereus group can survive in various ecological environments, and this ability is generally considered to be associated with their robust endospores, while the production of antimicrobial substances confers a double advantage for their survival and growth in different habitats (7).…”